Formation of polycyclic aromatic hydrocarbon via gas phase benzyne

Gas phase benzyne generated from the high temperature pyrolysis of phthalic anhydride is reduced to benzene. This newly formed benzene is then free to react further with more benzyne to yield more complex aromatic hydrocarbons.     

Characterization of trace organic contaminants in marine sediment from Yeongil Bay, Korea: 2. Dioxin-like and estrogenic activities

This study employed mechanism-specific in vitro bioassays to help characterize the occurrence and distribution of dioxin-like and estrogenic contaminants in sediment from Yeongil Bay, Korea. Approximately 85% of the sediments tested induced significant dioxin-like activity in the H4IIE-luc bioassay, while approximately 50% induced significant estrogenic activity in the MVLN bioassay. Instrumentally-derived estimates of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17beta-estradiol equivalents tended to underestimate the magnitude of response observed in the bioassays, suggesting that compounds detected by chemical analysis did not account for all the activity associated with Yeongil Bay sediments, or that non-additive interactions were occurring. The greatest dioxin-like and estrogenic activity was associated with the mid-polarity Florisil fractions (F2) expected to contain polycyclic aromatic hydrocarbons (PAHs) as well as chlorinated dioxins and furans. As in previous studies of Korean coastal sediment, more polar fractions (F3) generated more modest responses both in terms of magnitude and the number of samples responding.     

Perfluorinated chemicals in relation to other persistent organic pollutants in human blood

In order to evaluate blood levels of some perfluorinated chemicals (PFCs) and compare them to current levels of classical persistent organic pollutants (POPs) whole blood samples from Sweden were analyzed with respect to 12 PFCs, 37 polychlorinated biphenyls (PCBs), p,p'-dichlorodiphenyl-dichloroethylene (DDE), hexachlorobenzene (HCB), six chlordanes and three polybrominated diphenyl ethers (PBDEs). The median concentration, on whole blood basis, of the sum of PFCs was 20-50 times higher compared to the sum of PCBs and p,p'-DDE, 300-450 times higher than HCB, sum of chlordanes and sum of PBDEs. Estimations of the total body amount of PFCs and lipophilic POPs point at similar body burdens. While levels of for example PCBs and PBDEs are normalized to the lipid content of blood, there is no such general procedure for PFCs in blood. The distributions of a number of perfluorinated compounds between whole blood and plasma were therefore studied. Plasma concentrations were higher than whole blood concentrations for four perfluoroalkylated acids with plasma/whole blood ratios between 1.1 and 1.4, whereas the ratio for perflurooctanesulfonamide (PFOSA) was considerably lower (0.2). This suggests that the comparison of levels of PFCs determined in plasma with levels determined in whole blood should be made with caution. We also conclude that Swedish residents are exposed to a large number of PFCs to the same extent as in USA, Japan, Colombia and the few other countries from which data is available today.     

Melamine-based organoclay to sequester atrazine

Sequestration of aqueous atrazine by organoclays prepared from the surfactant 6-piperazin-1-yl-N,N'-bis-(1,1,3,3-tetramethyl-butyl)-(1,3,5)triazine-2,4-diamine and Gonzales bentonite was assessed using 14C-labeled atrazine. Organoclays with varying ratios of surfactant to clay were evaluated with respect to their ability to sequester atrazine from an aqueous solution. Organoclays containing 100-200 g kg-1 surfactant on a total weight basis provided the most efficient adsorption of atrazine, with apparent KOC values exceeding 5000 l kg-1 at these loading fractions. Less than 12% of sequestered atrazine was released during four sequential day long washings, supporting our expectation that the majority of the reaction of atrazine with the surfactant lead to irreversible chemical bond formation through nucleophilic aromatic substitution.     

Brominated flame retardant concentrations and trends in abiotic media

BFR burdens in abiotic media have been less studied than in biota, despite their essential value as an aide to identifying sources, temporal and geographic trends and exposure routes. Many polymer products consist of several percent by weight of BFRs. Global trade in these can result in rapid and wholesale BFR movement. Loss from in-use products of nonreactive BFRs may be important, particularly in respect to indoor exposure. In the case of BDE-209, discharges from publicly owned treatment works may be substantial. BFR burdens in air, water and sewage sludge respond rapidly to changes in environmental BFR inputs. PBDEs have been the most widely studied. In many locales PBDE burdens in these media now surpass those of PCBs. Air and water near sources and urban areas are typically enriched relative to rural locales. The more volatile PBDEs dominate in the vapor phase, while BDE-209 typically predominates on particulates. Evidence exists for long-range transport of the more volatile PBDEs. A greater diversity of BFRs (mostly PBDEs, HBCD and TBBP-A) has been detected in sewage sludges. Land application of these sludges on agricultural fields is one conduit for soil contamination. In general, environmental concentrations of BDE-209 appear to be increasing, while penta-BDE burdens in Europe may have peaked. Sediments function as longer-term integrators of environmental burdens. Concentrations of common BFRs therein may be substantial near point sources. Evidence for debromination in the environment has been limited to date. However, some laboratory and field observations suggest it is possible to a limited extent.